dana bash breaks it down starting in october of 1972. >> reporter: election year 1972. the raging unpopular war in vietnam consumed the bitter campaign battle between president nixon and george mcgovern. suddenly on october 26th, 12 days before the election, vietnam negotiator henry kissinger made a surprise declaration, believed to cement nixon's front-runner status. >> we believe that peace is at hand. >> reporter: it was the first so-called october surprise, a late in the game campaign event with a significant impact on the election. >> in order to win re-election for nixon in 1972, they needed to end the vietnam war, and this was sort of the definitive statement. >> reporter: the most famous october surprise was in 1980, and the surprise was what did not happen. 52 u.s. hostages held in iran were not released before the election, despite president carter's efforts. instead, they were freed as soon as ronald reagan was inaugurated, setting off democratic suspicion never proven that reagan emissaries back channeled with iran to delay freeing the hostages and deny the